Silver-silicon alloy and process of making the same



Patented Sept. 27, 1927.

1,643,304 UNITED STATES PATENT OFFICE.

MICHAEL G. KORSUNSKY, or JACKSON HEIGHTS, 'NEW YORK, NOW 'BY JUDICIAL CHANGE or NAME MICHAEL enoner. CORSON, ASSIGNOB TO ELECTED METAL- LURGICAL COMPANY, A CORPORATION or wnsr VIRGINIA.

SIIiVER-SILICON ALLOY AND PROCESS OF MAKING THE SAME.

No Drawing. Application filed May 16,

The invention relates to alloys of silver and silicon with or without other components. Among the important advantages of the alloys are substantial freedom from tarnishing and improved wear-resisting quality, as compared with sterling silver.

As is well known, silver and its commercial alloys are very readily tarnished by the action of sulfur. They are also affected to a certain extent by atmospheric oxygen and moisture. This is particularly noticeable when the air is ozonized'by electrical storms.

, I have discovered that silicon, alloyed with silver or certain of its alloys, as hereinafter described, has the property of substantially preventing the formation of tarnishing deposits comprising silver sulfids, suboxids, or other compounds. The resistance to tarnishing agents appears to be due principally to the very considerable refine ment of the crystal structure or grain of the alloy caused by the silicon. The alloys of the present invention are resistant to tarnishing influences even after long standing in damp and ozonized air or in an atmosphere charged with hydrogen sulfid. The repeated polishing necessary to keep a bright surface on silverware, as heretofore made,is substantially eliminated when the new alloys are used.

The wear-resisting qualities of silver-silicon alloys are excellent. Although they are ductile and readily workable, they have a Brinnell hardness of to 80, as compared with about 32 for annealed or cast sterling silver.

Referring first to silver-silicon alloys without other components, the silicon should generally be present in amounts of from about 3% to 6%, silver 97% to 94%. With less than 3% silicon the alloy may tarnish under adverse conditions. With more than, 6% there is a tendency to excessive hardness and brittleness, due to a precipitation of large crystals of silicon, which may make the alloy unsuitable for some purposes.- The percentages of silver and silicon are sufliciently close to those of the eutectic alloy (about 5% Si, 95% A to insure a reed grain product su ciently homogeneous, strong, and ductile to be used for the desired urposes. p

I pre er to use one or more additional components in the alloy. In general these ing to cause segregation of the 1924.v Serial No. 713,851.

will be members of the group of metals characterized by the formation of a solid solut1 on w th silver. Cadmium, aluminum, zinc, tin, and antimony are the most important of these metals. In silver-silicon alloys containing a large amount of another metal, the requisite proportion of sili cOn may be less than 3%. It should not ordinarilybe less than 1.5%. i

The invention is not limited to precise proportlons of the components. By Way of example, advantageous results are obtained by including with silver and silicon from 2 to 30% cadmium, 1 to 8% tin, or 1 to10%' z1nc. Alloys containing about 40to 48% aluminum, 3 to 4% silicon, the remainder being silver, are very suitable for ornamental castings. The addition of a metal of the group indicated may .facilitate casting or have other desirable efi'ects. Fromi the commercial standpoint the use of these metals is also advantageous because it; reduces the cost of the alloy.

The alloys of the present invention may be cast, worked, and annealedin the same way as the silver alloys now in common use,

or according to other, suitable methods. g

For example, an alloy of the sterling type comprising silver 92 silicon 4%, and cadmium or tin 3 1. may be prepared: by fusion of the components at about 1000 C. The fusion should be carried out in a crucible made of sand, clay, or other material which will notimpart carbon to the alloy. Good quality graphite crucibles may be used without fear of carbon absor tion by the alloy. Carbon is to be avoided because tendsilicon in the form of silicon carbide.

into the molds is preferably between 870- 930 C. I prefer to melt my alloys under a flux composed of barium fluorid and calcium fluorid. A mixture of equal parts of these The temperature of the alloy when poured salts freezes just above the best pouring temperature and therefore ma serve as a tem-' perature control. Under 1: e conditions described the ingots are ordinarily homo eneous and substantially free from blowioles and silicon segregations. The color and metallic lustre are practically identical with those of pure silver.

The alloy may be cast as' ingots or into molds having the form of the desiredarticle.

proportion,

The ingots may be rolled into sheets adapted to be shaped by stamping or the like in the well known manner. If the alloy must be worked to a considerable extent, it may be annealed at frequent intervals, preferably by heating to about 650 C.

Thealloys of the present invention are adapted for use in the manufacture of plate, coin, jewelry, and in general for all purposes now served by silver or silver alloys. In addition, on account of their relatively high chemical resistance, strength, and stiffness, the new alloys will serve a number of industrial urposes for which priofi silver alloys have been generally unsuited. For example, stills and other chemical apparatus may be advantageously made from silver-si icon alloys of the type described herein.

My invention is based upon an investigation of the physical and chemical properties of silver-silicon alloys, and the resulting discovery of the important characteristics herein noted. So far as Iam aware, such alloys had not been considered prior to my invention, apart from theoretical investigations to determine their existence. The production of a substantially non-tarnishable, wear resistant, workable silver alloy is a new and valuable advance in the art. The invention is therefore defined broadly in the appended claims.

I claim:

I. As a new article of manufacture, an alloy containing silver in preponderating silicon in amount of from 1.5 to 6%, and 1 to 50% of a member of the group of metals characterized by the formation of a solid solution with silver.

2. As a new article of manufacture, an alloy consisting predominantly of silver and containing about 3 to 6% silicon and 1 to 50% of a member of the group of metals characterized by the formation of a solid solution with silver.

3. As a new article of manufacture, an alloy consisting predominantly of silver alloyed with 1.5 to 6% silicon and 2 to 30% cadmium.

4. As a new article of manufacture, a ste ling silver alloy having approximatel the composition 92.5% Ag, 4% Si, 3.5% d.

5. Process of making shaped bodies of silver-silicon alloy, comprising fusing the alloy ingredients under conditions precluding access of carbon, and casting the alloy.

6. Process of making-shaped bodies of silver-silicon alloy, comprising fusing the alloy ingredients under conditions precludmg access at a temperature of about 870930 G. into molds.

7 Process of making shapedbodies of silver-silicon alloy, comprisin fusing the alloy ingredients under conditions recluding access of carbon, pouring the a oy at a tem erature of about 870-930" G. into molds, wor ing the alloy and then annealing the molded alloy at a temperature of about 650 C. a

In testimony whereof, I aflix my signature.

MICHAEL G. KORSUNSKY.

of carbon, and pouring the alloy 

